Heat exchanger



Fb. 13, 1968 ROSMAN ET AL 3,368,617

HEAT EXCHANGER Filed Dec. 26, 1961 2 Sheets-Sheet 1 INVENTORS IRWIN E. ROSMAN ALBERT MALEK ATTORNEY United States Fatent C 3,368,617 IEAT EXCHANGER Irwin E. Rosman and Albert Malek, Woodland Hills, Calif., assignors to The Marquard't Corporation, Van Nuys, Calih, a corporation of California Filed Dec. 26, 1961, Ser. No. 161,840 8 Claims. (Cl. 165175) This invention relates to heat exchanger apparatus and more particularly to a heat exchanger including a plurality of contiguous tube plates having upstanding walls and cover plates forming duct-type headers which may be joined together on their low-temperature walls.

In the liquid air cycle engine of an aircraft, liquid hydrogen is passed through a heat exchanger in order to liquify incoming ambient air for use as an oxidant such heat exchangers are subject to large temperature gradients which result in high stresses warranting the use of heavy material, but must, on the other hand, be as light as possible to lessen the Weight of the aircraft,

In conventional heat exchangers employing a single tube plate and a single header for a number of rows of heat exchanger tubes, the header produces large forces which cause the tube sheet to bend so that the inner tubes are in compression and the outer tubes are in tension. To prevent this, a rather heavy tube plate must be utilized and the thin tubes must be welded to the heavy plate. In such a construction, the stress concentration will always be in the thin tube rather than in the heavy tube plate. Also, a thick tube plate will not give readily to permit changes in the length of the tubes because of changing temperatures. A thin tube plate has been utilized in other types of conventional heat exchangers where the pressures on opposite sides of the tube plate are equal, but the outer pressure wall must be heavy to contain the pressures so that no saving in weight will result. Also, in this structure, the cold coolant passing through the header causes it to contract. However, since the tube plate is not responsive to the cold coolant, it does not change dimension appreciably and thus, the tubes are bent upon a change in dimension of the header.

In the heat exchanger design of the present invention, not only are separate tube plates used for each row of tubes, but individual cover plates are also used and are joined to the tube plates by sidewalls forming headers which constitute separate, closed ducts for each row of tubes. These ducts are joined together only along their outer, low-temperature walls. With this design, the pressure stresses are uniformly distributed symmetrically about the tubes. The stress in the tube plate caused by multidirectional pressure duct loads will be equally distributed around the end of each single tube of each single row. Also, because of the internal pressure acting on the tube plate for each single row, each of the tubes will be only in tension since none of the bending or compressive forces described in the prior devices are present. Closing the headers with an outer, low temperature plate or wall which is not subjected to the internal heat within the heat exchanger permits welding so that a side passage tructure can be welded to the top plate in order to transmit the loading to the cooler plates instead of to the inner, high temperature plates.

In view of the foregoing factors and conditions characteristic of light weight heat exchangers, it is a primary object of the present invention to provide a new and improved heat exchanger not subject to the disadvantages enumerated above and having a plurality of contiguous tube plate including upstanding walls forming a closed duct with a contiguous cover plate especially designed and connected together on their low-temperature walls 3,358,517 Patented Feb. 13, 1968 "ice in such a manner that loading on the plates and tubes will be minimized.

Another object of the invention is to provide a heat exchanger of the type described wherein pressure stresses are uniformly distributed symmetrically about the heat exchanger tubes.

Still another object of the invention is to provide a heat exchanger of the type described wherein the heat exchanger tubes are not subject to bending or compressive forces induced by loads from the tube plate.

A further object of this invention is to provide a heat exchanger of the type described wherein the heat exchanger headers are closed by a top plate which is not subjected to the internal heat within the heat exchanger.

Another object of the invention is to provide a heat exchanger having a plurality of contiguous cover plates forming outer, low-temperature walls, a plurality of contiguous tube plates forming inner, high-temperature walls, upstanding, impervious side walls connecting a longitudinal edge of each tube plate to a corresponding superjacent edge of each cover plate to form a closed duct, and means for aflixing a plurality of closed ducts together in side-byside, abutting relationship in such a manner that they will have a rigid connection along the outer, low-temperature walls and remain unconnected along their inner, hightemperature walls.

These and other more specific objects will appear upon reading the following specification and claims and upon considering in connection therewith the attached drawings to which they relate.

Referring now to the drawings in which preferred embodiments of the invention are illustrated:

FIGURE 1 is a perspective view, with parts broken away, of a heat exchanger tube and header assembly of the invention;

FIGURE 2 is a partial view, in perspective, of two tube and header assemblies joined together by welding;

FIGURE 3 is a partial View, in perspective, of two tube and header assemblies joined together by a fiat lip;

FIGURE 4 is a partial view, in perspective, of two tube and header assemblies joined together by upright joining strips;

FIGURE 5 is a partial view, in perspective, of two tube and header assemblies joined together by an offset lip; and

FIGURE 6 is a perspective view, with parts broken away of a heat exchanger assembly.

Referring again to the drawings, a heat exchanger assembly, constituting the present invention, generally designated 10 (FIGURE 6), includes a plurality of individual tube and header assemblies 11 (FIGURE 1) having upper and lower headers 12 and 14, respectively. A plurality of tubes 16 place the headers 12 and 14 in hydraulic communication with each other. The individual tube and header assemblies 11 are joined together in a manner to be hereinafter described and are connected to a fluid supply duct 17 which brings a fluid, such as air, into heat exchange relation with the tube and header assemblies 11. Fluid is admitted to the supply duct 17 through an inlet conduit 17a.

Each header 12 and 14 includes a tube plate or hightemperature inner wall 18, a pair of upstanding sidewalls 20 and 21, respectively, and a cover plate or low-temperature outer wall 22. Each tube plate 18 includes tube receiving apertures 19 into which an end of the tube 16 is placed so that the upper header 12 may be joined to the lower header 14 to form the integral tube and header assembly 11 which may be used as an elemental heat exchanger unit. A number of these elemental units 11 may be combined, in a manner to be hereinafter described, to constitute a complete heat exchanger. The ends of the tubes 16 may be retained in the apertures 19 3 by any suitable means such that tensile separation loads of the headers 12 and 14 will be transmitted by the tubes 16.

In the embodiment shown in FIGURE 1, the cover plate 22 includes an integral, longitudinally extending, lip 23 which is offset upwardly in such a manner that a plurality of heat exchanger headers and tube assemblies 11 can be placed in side-by-side, abutting relationship, and rigidly connected together by means of the lip 23. The sidewalls 2t and 21 of this embodiment include inturned flanges 24 and 25 to which the cover plate 22 is rigidly afiixed.

Referring now to FIGURE 2, an extruded header 12a includes a tube plate 18a, upstanding sidewalls 20a and 21a, and a cover plate 22a which form unitary, rectangular ducts. The tube plate 18a includes apertures 19:: which receive one end of the tubes 16a. In this embodiment, a plurality of tube and header assemblies 11a may be joined together along their low-temperature walls 22a by welding, as shown.

The embodiment of the invention shown in FIGURE 3 includes a tube plate 185, upstanding Walls 2% and 21b, and a cover plate 22b. The wall 2% is substantially straight and the wall 21b includes an in-turned flange 25b. The cover plate 22b includes a longitudinally extending, down-turned flange 26b adapted to abut the upper, inner edge of Wall 20b and is rigidly atfixed thereto. The plate 22b is supported b the in-turned flange 25b and may be secured thereto by any suitable means, not shown. The plate 22b is wider than the tube plate 181; so that the longitudinal edge remote from flange 26b extends beyond the wall 21b forming a flat lip 23b which serves as the joining strip to join a plurality of header and tube assemblies 1115 together along their outer, lowtemperature walls 22b.

The embodiment shown in FIGURE 4 includes an extruded header 120 having a tube plate 13c, sidewalls Ztlc and 210, and an integral top plate or low-temperature wall 220. Upstanding flanges 230 include bolt receiving apertures 26c and constitute joining strips for joining a plurality of tube and header assemblies 11c together along their low-temperature walls 22c by means of bolts 270.

The embodiment shown in FIGURE includes an extruded header 12d having an integral bottom plate 18d, sidewalls 20d and 21d and a top plate 22d. A plurality of tube and header assemblies 11d are joined together by means of an integral, stepped lip 23d.

Referring again to FIGURE 6, a plurality of tube and header assemblies 11d are joined together in side-byside, abutting relationship by rigidly connecting the lip 23d of one assembly 11d to the low-temperature wall 22d of and adjacent tube and header assembly lid to form a heat exchanger cell 29.

An end plate 39 is used to seal each end of the heat exchanger cell 29 and the individual tube and header assemblies list are placed in hydraulic communication with each other through alternating inlet and outlet manifolds 31 and 32, respectively. A coolant inlet conduit 34 is connected to a first inlet manifold 31a through nipples 36 and a spent coolant outlet conduit 38 is connected to the end outlet manifold 32a by means of nipples 40. A series of U-bends 42 connect the intermediate manifolds 31b and 32b together.

The heat exchanger cell 29 is placed in a heat exchanger system by enclosing it in the fluid supply duct 17. The duct 17 is attached to the cell 29 by rigidly affixing the edges of the duct 17 to the low temperature Walls 22d, only. The walls 22d then carry the multidirectional pressure duct loads. With this construction, the inner, high temperature walls 18d carry tube loads, only.

In operation, a suitable coolant such as liquid hydrogen, flows into the heat exchanger cell 29 through the conduit 34 and circulates back and forth through the inlet and outlet manifolds 31 and 32 and is discharged from the cell through outlet conduit 38.

The fluid to be cooled is admitted to the supply duct 17 through its inlet conduit 17a, passes around the tubes 11d losing heat to the coolant, and then leaves the system through an outlet conduit, not shown.

While the particular heat exchangers herein shown and described in detail are fully capable of obtaining the objects and providing the advantages hereinbefore stated, it is to be understood that they are merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as defined in the appended claims.

We claim:

1. A heat exchanger comprising:

a heat exchanger cell including a plurality of tube and header assemblies having outer, low-temperature walls forming closed ducts with inner, high-tempera ture walls, said tube and header assemblie being rigidly joined together only along their outer, lowtemperature walls in side-by-side, abutting relationship; sealed duct housing said cell, said sealed duct being rigidly afiixed to said cell only along said outer low-temperature walls;

means placing said tube and header assemblies in hydraulic communication with each other;

first conduit means for admitting coolant to, and withdrawing spent coolant from, said cell; and

second conduit means for circulating a fluid to be cooled through said sealed duct into heat exchanger relation with said cell.

2. A heat exchanger capable of withstanding high structural stress resulting from large temperature gradients comprising:

a plurality of elemental heat exchanger units, each unit comprising a plurality of tubes connecting between two longitudinally extending headers at opposite ends thereof,

each header comprising a duct having an outer wall and a tube plate containing tube receiving apertures in which the ends of said tubes are separately received to join two of said headers,

the headers at each end of said units being assembled in side-by-side, abutting relationship to form closed sides at opposite ends of said tubes, the fluid flowing over said tubes producing a temperature differential between said tube plates and said outer walls, and

means for rigidl securing each adjacent pair of headers together solely at the outer walls of the headers in order to distribute stresses symmetrically about the tubes.

3. A heat exchanger capable of withstanding high structural stress resulting from large temperature gradients comprising:

a plurality of elemental heat exchanger units, each unit comprising a plurality of tubes connecting between two longitudinally extending headers at opposite ends thereof,

each header comprising a tube plate, a pair of side walls and an outer cover wall to form a fluid duct, each of said tube plates containing tube receiving apertures in which the ends of said tubes are separately received to join said two headers,

the headers at each end of said units being assembled with the side walls thereof positioned adjacent to one another to form closed sides at opposite ends of said tubes, the fluid flowing over said tubes producing a temperature differential between said tube plates and said cover Walls, and

reans for rigidly securing each adjacent pair of headers together solely at the outer cover walls of the headers in order to distribute stresses symmetrically about the tubes.

4. A heat exchanger as defined in claim 3 wherein said tube plates are a higher temperature than said cover walls so that the loading stress on said heat exchanger is carried by the low-temperature cover walls.

5. A heat exchanger as defined in claim 3 wherein said securing means comprises a weld between adjacent edges of said cover walls.

6. A heat exchanger as defined in claim 3 wherein said securing means comprises an outwardly, angularly extending flat lip on one edge of each of said cover walls overlapping and secured to the cover wall of an adjacent header.

7. A heat exchanger as defined in claim 3 wherein said securing means comprises,

upstanding flanges at opposite edges of each of said cover walls, and

means for securing adjacent flanges together along the lengths thereof.

8. A heat exchanger as defined in claim 3 wherein said securing means comprises, an outwardl extending, stepped lip on one edge of each of said cover walls overlapping and secured 5 to the cover wall of an adjacent header.

References Cited UNITED STATES PATENTS 2,044,457 6/1936 Young 165176 10 2,602,648 7/1952 Martel 165172 2,642,271 6/1953 Berger 165172 FOREIGN PATENTS 7,048 2/1905 Great Britain.

15 ROBERT A. OLEARY, Primary Examiner.

CHARLES SUKALO, Examiner.

T. W. STREULE, Assistant Examiner. 

1. A HEAT EXCHANGER COMPRISING: A HEAT EXCHANGER CELL INCLUDING A PLURALITY OF TUBE AND HEADER ASSEMBLIES HAVING OUTER, LOW-TEMPERATURE WALLS FORMING CLOSED DUCTS WITH INNER, HIGH-TEMPERATURE WALLS, SAID TUBE AND HEADER ASSEMBLIES BEING RIGIDLY JOINED TOGETHER ONLY ALONG THEIR OUTER, LOWTEMPERATURE WALLS IN SIDE-BY-SIDE, ABUTTING RELATIONSHIP; A SEALED DUCT HOUSING SAID CELL, SAID SEALED DUCT BEING RIGIDLY AFFIXED TO SAID CELL ONLY ALONG SAID OUTER LOW-TEMPERATURE WALLS; MEANS PLACING SAID TUBE AND HEADER ASSEMBLIES IN HYDRAULIC COMMUNICATION WITH EACH OTHER; FIRST CONDUIT MEANS FOR ADMITTING COOLANT TO, AND WITHDRAWING SPENT COOLANT FROM, SAID CELL; AND SECOND CONDUIT MEANS FOR CIRCULATING A FLUID TO BE COOLED THROUGH SAID SEALED DUCT INTO HEAT EXCHANGER RELATION WITH SAID CELL. 